As a field, we have a limited understanding of what teachers do, what motivates them, and how they learn (Kennedy, 2016). Here, we develop a grounded framework of inquiry-based teaching in mathematics classrooms by beginning with primary evidence of teachers teaching. We seek to articulate an evidence-based account of teachers' functional (rather than aspirational) concerns so that those who support teachers -- such as curriculum writers, professional learning specialists, coaches, and teacher educators -- can ground their support in the realities of the work of teaching. Our research question is: "What are the functional concerns that shape teachers' decision-making in-the-moments of teaching?". [For the complete proceedings, see ED630210.]